Schedule II - Aflac Incorporated (Parent Only) - Summary of Notes Payable (Parenthetical) (Detail)	Dec. 31, 2012 8.50% senior notes due May 2019	Dec. 31, 2011 8.50% senior notes due May 2019	May 31, 2009 8.50% senior notes due May 2019 USD ($)	Dec. 31, 2012 6.45% senior notes due August 2040 USD ($)	Dec. 31, 2011 6.45% senior notes due August 2040	Aug. 31, 2010 6.45% senior notes due August 2040 USD ($)	Dec. 31, 2012 6.90% senior notes due December 2039 USD ($)	Dec. 31, 2011 6.90% senior notes due December 2039	Dec. 31, 2009 6.90% senior notes due December 2039 USD ($)	Dec. 31, 2012 3.45% senior notes due August 2015	Dec. 31, 2011 3.45% senior notes due August 2015	Aug. 31, 2010 3.45% senior notes due August 2015 USD ($)	Dec. 31, 2012 2.65% senior notes due February 2017 USD ($)	Jul. 31, 2012 2.65% senior notes due February 2017 USD ($)	Feb. 29, 2012 2.65% senior notes due February 2017 USD ($)	Dec. 31, 2012 4.00% senior notes due February 2022 USD ($)	Feb. 29, 2012 4.00% senior notes due February 2022 USD ($)	Dec. 31, 2012 5.50% subordinated notes due September 2052 USD ($)	Oct. 31, 2012 5.50% subordinated notes due September 2052 USD ($)	Sep. 30, 2012 5.50% subordinated notes due September 2052 USD ($)	Dec. 31, 2012 2.26% yen-denominated Uridashi notes due September 2016 JPY (¥)	Dec. 31, 2011 2.26% yen-denominated Uridashi notes due September 2016 JPY (¥)	Sep. 30, 2006 2.26% yen-denominated Uridashi notes due September 2016 JPY (¥)	Dec. 31, 2012 1.47% yen-denominated Samurai notes due July 2014 JPY (¥)	Dec. 31, 2011 1.47% yen-denominated Samurai notes due July 2014 JPY (¥)	Jul. 31, 2011 1.47% yen-denominated Samurai notes due July 2014 JPY (¥)	Dec. 31, 2011 1.87% yen-denominated Samurai notes due June 2012 JPY (¥)	Jun. 30, 2007 1.87% yen-denominated Samurai notes due June 2012 JPY (¥)	Dec. 31, 2012 1.84% yen-denominated Samurai notes due July 2016 JPY (¥)	Dec. 31, 2011 1.84% yen-denominated Samurai notes due July 2016 JPY (¥)	Jul. 31, 2011 1.84% yen-denominated Samurai notes due July 2016 JPY (¥)	Dec. 31, 2012 Variable interest rate yen-denominated Samurai notes due July 2014 JPY (¥)	Dec. 31, 2011 Variable interest rate yen-denominated Samurai notes due July 2014 JPY (¥)	Jul. 31, 2011 Variable interest rate yen-denominated Samurai notes due July 2014 JPY (¥)	Dec. 31, 2012 3.60% yen-denominated loan due July 2015 JPY (¥)	Dec. 31, 2011 3.60% yen-denominated loan due July 2015 JPY (¥)	Dec. 31, 2012 3.00% yen-denominated loan due August 2015 JPY (¥)	Dec. 31, 2011 3.00% yen-denominated loan due August 2015 JPY (¥)	Dec. 31, 2012 Parent Company 8.50% senior notes due May 2019	Dec. 31, 2011 Parent Company 8.50% senior notes due May 2019	Dec. 31, 2012 Parent Company 6.45% senior notes due August 2040 USD ($)	Dec. 31, 2011 Parent Company 6.45% senior notes due August 2040	Dec. 31, 2012 Parent Company 6.90% senior notes due December 2039 USD ($)	Dec. 31, 2011 Parent Company 6.90% senior notes due December 2039	Dec. 31, 2012 Parent Company 3.45% senior notes due August 2015	Dec. 31, 2011 Parent Company 3.45% senior notes due August 2015	Dec. 31, 2012 Parent Company 2.65% senior notes due February 2017 USD ($)	Dec. 31, 2012 Parent Company 4.00% senior notes due February 2022 USD ($)	Dec. 31, 2012 Parent Company 5.50% subordinated notes due September 2052	Dec. 31, 2012 Parent Company 2.26% yen-denominated Uridashi notes due September 2016 JPY (¥)	Dec. 31, 2011 Parent Company 2.26% yen-denominated Uridashi notes due September 2016 JPY (¥)	Dec. 31, 2012 Parent Company 1.47% yen-denominated Samurai notes due July 2014 JPY (¥)	Dec. 31, 2011 Parent Company 1.47% yen-denominated Samurai notes due July 2014 JPY (¥)	Dec. 31, 2012 Parent Company 1.87% yen-denominated Samurai notes due June 2012 JPY (¥)	Dec. 31, 2011 Parent Company 1.87% yen-denominated Samurai notes due June 2012 JPY (¥)	Dec. 31, 2012 Parent Company 1.84% yen-denominated Samurai notes due July 2016 JPY (¥)	Dec. 31, 2011 Parent Company 1.84% yen-denominated Samurai notes due July 2016 JPY (¥)	Dec. 31, 2012 Parent Company Variable interest rate yen-denominated Samurai notes due July 2014 JPY (¥)	Dec. 31, 2011 Parent Company Variable interest rate yen-denominated Samurai notes due July 2014 JPY (¥)	Dec. 31, 2012 Parent Company 3.60% yen-denominated loan due July 2015 JPY (¥)	Dec. 31, 2011 Parent Company 3.60% yen-denominated loan due July 2015 JPY (¥)	Dec. 31, 2012 Parent Company 3.00% yen-denominated loan due August 2015 JPY (¥)	Dec. 31, 2011 Parent Company 3.00% yen-denominated loan due August 2015 JPY (¥)
Condensed Financial Statements, Captions [Line Items]
Notes payable, interest rate	8.50%	8.50%		6.45%	6.45%		6.90%	6.90%		3.45%	3.45%		2.65%	2.65%	2.65%	4.00%	4.00%	5.50%	5.50%	5.50%	2.26%	2.26%		1.47%	1.47%	1.47%	1.87%		1.84%	1.84%	1.84%	1.34%	1.34%	1.475%	3.60%	3.60%	3.00%	3.00%	8.50%	8.50%	6.45%	6.45%	6.90%	6.90%	3.45%	3.45%	2.65%	4.00%	5.50%	2.26%	2.26%	1.47%	1.47%	1.87%	1.87%	1.84%	1.84%	1.34%	1.34%	3.60%	3.60%	3.00%	3.00%
Notes payable, principal amount			$ 850,000,000	$ 450,000,000		$ 450,000,000	$ 400,000,000		$ 400,000,000			$ 300,000,000	$ 650,000,000	$ 250,000,000	$ 400,000,000	$ 350,000,000	$ 350,000,000	$ 450,000,000	$ 50,000,000	$ 450,000,000	¥ 8,000,000,000	¥ 8,000,000,000	¥ 10,000,000,000	¥ 28,700,000,000	¥ 28,700,000,000	¥ 28,700,000,000	¥ 26,600,000,000	¥ 30,000,000,000	¥ 15,800,000,000	¥ 15,800,000,000	¥ 15,800,000,000	¥ 5,500,000,000	¥ 5,500,000,000	¥ 5,500,000,000	¥ 10,000,000,000	¥ 10,000,000,000	¥ 5,000,000,000	¥ 5,000,000,000			$ 450,000,000		$ 400,000,000				$ 650,000,000	$ 350,000,000		¥ 10,000,000,000	¥ 10,000,000,000	¥ 28,700,000,000	¥ 28,700,000,000	¥ 30,000,000,000	¥ 30,000,000,000	¥ 15,800,000,000	¥ 15,800,000,000	¥ 5,500,000,000	¥ 5,500,000,000	¥ 10,000,000,000	¥ 10,000,000,000	¥ 5,000,000,000	¥ 5,000,000,000